The purpose of this study is to better understand the relationship between bipolar disorder, body weight, and inflammation in the body. People with bipolar depression will be offered a place in a pilot study looking to see if the antibiotic minocycline added to current psychiatric medications has an effect on mood. A separate consent form will be provided for the pilot study. Numerous studies have documented the presence of altered immune function and elevation of inflammatory markers in patients with depression. Studies suggest that major depression is accompanied by immune dysregulation and activation of the inflammatory response system. While a small number of studies have found elevated inflammatory markers in bipolar mania, very little has been reported about inflammation in bipolar depression, and none of these studies have addressed the relationship of inflammatory markers with obesity in bipolar disorder.